1. Field of the Invention
The present invention relates to a producing apparatus for decomposing and converting high boiling point chlorosilanes-containing materials (hereinafter, referred to as polymer) generated in a polycrystalline silicon producing process and in a trichlorosilane producing or converting process into trichlorosilane, and more particularly, to an apparatus for producing trichlorosilane by decomposing a polymer produced in a chlorination process, a polymer separated from an exhaust gas of a reaction process of polycrystalline silicon, or a polymer produced in a conversion process for producing trichlorosilane from silicon tetrachloride in an exhaust gas, and a method for producing trichlorosilane.
Priority is claimed on Japanese Patent Application No. 2008-201863, filed on Aug. 5, 2008, the content of which is incorporated herein by reference.
2. Description of Related Art
High-purity polycrystalline silicon used for semiconductor materials are mainly produced by the Siemens process using trichlorosilane (SiHCl3: TCS) and hydrogen as the raw materials. The Siemens process is a process of introducing a gas mixture of trichlorosilane and hydrogen into a reactor so as to come in contact with a glowing silicon rod, and depositing silicon on the surface of the silicon rod due to the hydrogen reduction and thermal decomposition of trichlorosilane at high temperature. For the high-purity trichlorosilane introduced into the reactor, for example, high-purity trichlorosilane obtained by distilling and purifying crude trichlorosilane obtained through a chlorination process is used. The chlorination process is a process for introducing metallurgical silicon and hydrogen chloride into a fluidizing chlorination furnace so as to react with each other and produce crude trichlorosilane using the chlorination of silicon.
In the producing of polycrystalline silicon, gases discharged from the reactor include unreacted trichlorosilane, hydrogen chloride, silicon tetrachloride (STC) as a byproduct, and chlorosilanes (referred to as high boiling point chlorosilanes) having higher boiling points than silicon tetrachlorides such as tetrachlorodisilane (Si2H2Cl4) and hexachlorodisilane (Si2Cl6) (refer to WO02/012122). In addition, crude trichlorosilane can be produced from silicon tetrachloride and hydrogen in the discharged gas by using a converter (conversion process). The distilled and purified crude trichlorosilane obtained in the conversion process have been reused. Gas produced in the chlorination furnace and the converter contains hydrogen chloride, silicon tetrachloride, and high boiling point chlorosilanes in addition to trichlorosilane.
Conventionally, polymers are produced when the gas produced in the chlorination furnace or in the converter, or the gas discharged from the reactor, is collected and distilled. These polymers should be hydrolyzed and disposed of. Accordingly, there is a problem in that costs involved in the hydrolysis and waste disposal are expensive.
In addition, a method is known for returning polymers generated in the producing of polycrystalline silicon to a fluid reaction container to be separated and using the separated polymers to produce trichlorosilane (refer to JP-A-01-188414). However, in this method, silicon powder supplied to a fluidizing reactor is mixed with polymers, so that there are problems in that flowability of the silicon powder is degraded, and the conversion ratio of the polymer into chlorosilane is reduced.